Process of producing key units wherein marking on their tops made of light-transmitting material can be completed later on

ABSTRACT

A method is provided for marking a key top made of a translucent material with a character, a symbol, or the like, and a process is provided for quickly producing an illumination key unit. The inside of a transparent plastic key top is irradiated intermittently with focused laser light having a wavelength belonging to near infrared region of 1064 nm or less, visible region or near ultraviolet region to form an aggregation of multiple fine carbonization black points and an aggregation of points whitened by fine cracks or bubbling representing a character, a symbol, or the like. After a process capable of being carried out without determining a destination has ended, production is interrupted temporarily or ended and marking is performed by irradiating the top surface of the key top with laser light upon determination of a character, a symbol, or the like, related with the destination.

This application is a U.S. National Phase Application under 35 USC 371of International Application JP/JP2003/16770 filed Dec. 25, 2003.

TECHNICAL FIELD

The present invention relates to an illuminated key unit useful as anindicator and controller of mobile devices such as portable telephonesand personal digital assistant (PDA) devices and other generalmachinery, wherein the process for plotting characters, symbols, etc. ineach key of the key unit can be completed after their respectivedestinations were decided.

BACKGROUND ART

The key unit is a kind of element constituting a mobile device and has amultiplicity of keys (push buttons) for operating switches,respectively, assembled and arranged on the surface of a sheet. Each keyis composed of a key pad which is made of a soft rubber or athermoplastic elastomer and a key top which is made of a rigid materialand is attached onto the surface of the key pad. The key pad has aprojection for pressing the switch (so-called “pusher”) formed on therear face. The keys in each horizontal row are connected to each otherthrough the key pad. Since each key is illuminated by a light sourceprovided under the key pad (referred to as “illuminated key”),light-transmitting materials are used for the key top and the key pad.An illuminated key switch is fabricated if a circuit board containinglight sources and having switch elements arranged to oppose therespective switch-pressing projections of the associated keys is broughtinto intimate contact with the lower face of the thus constituted keyunit.

When an illuminated key unit is to be produced, key tops and a key padare formed in separate steps respectively, and then they are assembledby bonding them together with an adhesive. Alternatively, key tops areformed first and are inserted into an injection mold to form a key padby means of insert molding. It is necessary to plot on the key topscharacters, symbols, etc. representing the functions of the respectivekeys. This step is referred to as “marking.” Generally, marking isapplied, for example, to the upper face (referred also to as “top face”)or lower face (bottom face) of each key top, or inside the key top. Whenmarking is to be applied to the top face, measures should be taken tosecure abrasion resistance of the characters, symbols, etc. marked onthe key top. On the other hand, the key tops may be opaque, and markingcan be carried out after bonding of the key tops to the key pad. Whenmarking is to be applied to the bottom face, it is essential that thekey top is transparent and that marking should be completed before thekey tops are bonded to the key pad. To that end, the content of thecharacters, symbols, etc. to be marked must be defined before bonding ofthe key tops to the key pad.

While mobile devices including portable telephones are shipped todifferent language regions of all over the world, the days counting fromdetermination of the destination to shipping is extremely limited. Of anumber of elements constituting a mobile device, those elementsexcluding the key unit which are not related to the language used in thedestination can be assembled before the destination is determined.However, in the case of key unit, although some markings including thoseof numerical characters which are not related to the relevant languagecan be applied beforehand, it is impossible to apply final marking andcomplete production of the key unit in the state where the language isnot determined and there is still any unconfirmed element in the contentof the characters, symbols, etc. to be marked. Nevertheless, it is toolate to start production of key units after determination of thedestination, whereas stock production of key units in many differentlanguages beforehand leads to glut, disadvantageously.

The problems described above are only some of those generally observablein the system of build-to-order manufacturing, and there are someconventional technologies directed to solving similar problems. Forexample, in the patent literatures listed below, Patent Literature 1relates to curtailment of lead time; Patent Literature 2 relates toinformation service of delivery schedule according to few-day base; andPatent Literature 3 relates to utilization of parts lists per model:

-   Patent Literature 1:-   Unexamined Japanese Patent Publication (Kokai) No. 2002-202805-   Patent Literature 2:-   Unexamined Japanese Patent Publication (Kokai) No. 2002-244711-   Patent Literature 3:-   Unexamined Japanese Patent Publication (Kokai) No. 2003-015722

A first object to be attained by the present invention is to provide akey top, which permits setting up of the content of characters, symbols,etc. to be plotted on the key top at any time without being subject tolimitations of other steps of key unit assembly and which is marked withcharacters, symbols, etc. such that they have sufficient abrasionresistance and also to provide a marking method for such purposes.

A second object to be attained by the present invention is to find out amaterial for forming key tops of illuminated key units, which canimpart, when marking is applied to the top face of each key top,sufficient abrasion resistance to characters, symbols, etc. marked onthe top face of the key top, as well as, to provide a marking method forsuch purposes and also to find out a method of marking the key top.

A third object to be attained by the present invention is to find out aprocess for producing an illuminated key unit, which enables completionof the key unit as soon as possible once the destination is determined.

DISCLOSURE OF THE INVENTION

The marking method referred to in the above first object includes thelaser method, the blasting method and the impregnation printing method.According to the laser method, the object can be attained by thetechnique shown in FIGS. 1 and 2. More specifically, in this markingmethod, a laser beam having a wavelength of 1064 nm or less in theinfrared, visible or near ultraviolet region is irradiatedintermittently onto a plastic key while the laser beam is focused on adesired position inside the key to form therein an assemblage of amultiplicity of fine carbonized black spots or an assemblage of whitespots formed by fine cracks and the like to indicate thereby acharacter, a symbol or the like. According to this marking method, thecontent of the character, symbol, etc. can be set up at any time withoutbeing subject to limitations of other steps in the key unit assembly.

There are two main reasons for using a laser beam having a wavelength of1064 nm or less in the above laser marking method: the first reason isthat the shorter the wavelength is, the higher becomes the energy of thelaser beam relative to longer-wavelength laser beams, provided that theyare of the same amplitude; the second reason is that infrared, visibleor near ultraviolet light with a short wavelength can be converged witha lens to easily achieve a spot diameter of 30 nm or less, so that sucha laser beam is suitable for forming fine carbonized black spots, whitespots of fine cracks or white spots obtained by foaming (foaming byseparation of side chains of the resin).

However, in the case where infrared (wavelength 10.6 μm) radiated from aCO₂ laser is to be utilized as the marking method, the spot diametercannot be narrowed fully to be unable to form fine carbonized blackspots and the like, and if the input power is increased unduly, theplastic keys are melted by the temperature rise, resulting in thefailure of achieving competent marking.

According to the blasting marking method, in an illuminated key unithaving a key pad made of a light-transmitting elastomer and glass orplastic key tops bonded onto to the key pad, marking is applied byblasting fine abrasive particles at a high speed against the top face ofeach glass or plastic key top. In attaining the above object of thepresent invention, the blasting technique may be any of masked blastingusing a mask and maskless blasting using no mask.

According to the impregnation printing marking method, marking isapplied by means of impregnation printing to the top face of each keytop or to the top face of each key top laminated with a resin film.

In order to attain the second object described above, the illuminatedkey unit according to the present invention contains a key pad made of alight-transmitting rubber or thermoplastic elastomer (hereinafterreferred to as “light-transmitting key pad”) and key tops bonded to thekey pad, wherein each key top is covered on the surface with amultilayer film, which can be printed on by irradiation of a laser beam.A laser beam is irradiated onto the top face of each key top to applythereto marking of necessary characters, symbols, etc. The thus markedcharacters, symbols, etc. inside the multilayer film neither come offnor disappear even by application of friction and the like, realizingexcellent abrasion resistance.

It should be noted here that the term “light-transmitting” used in thepresent invention is intended to mean in contrast to “fullylight-blocking” and contains the meaning of translucent in the colored,colorless or milky state.

As the multilayer film which can be printed on by irradiation of a laserbeam described above, for example, the one as disclosed in the pamphletof PCT Publication No. 02/30677 (WO0230677) can be used. In thepamphlet, a film having a multilayer structure is disclosed, containinga transparent plastic film with a metal vapor-deposited film formed onthe lower face and a colored layer formed with some distance securedfrom the metal vapor-deposited film. By irradiating a laser beam ontothe multilayer film to remove the metal vapor deposited film into adesired pattern, the light reflected by the colored layer or the lighttransmitted through the colored layer can be seen from the top of themultilayer film through the pattern formed in the metal vapor-depositedfilm (see FIG. 17).

In order to attain the third object described above, in the process ofproducing the key unit, production is interrupted once to form asemi-finished product in the state where all of the steps includingassembling which are implementable without determination of thedestination are finished beforehand. More specifically, the key topseach covered on the surface with the multilayer film are bonded to thelight-transmitting key pad to complete assembling of the key unit. Forthe semi-finished product, what is remaining in this state is only thestep of applying marking onto the top face of each key top. As soon ascharacters, symbols, etc. related to the destination are defined,application of final markings including the characters, symbols, etc.related to the destination is carried out by irradiating a laser beamonto the top face of the key top, thus providing a process of completingthe key unit in the shortest period of time after determination of thedestination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing the constitution of an SHG YAGlaser (green; output:053 μm) using nonlinear crystal which can beemployed for marking;

FIG. 2 shows schematic diagrams explaining a first embodiment of thepresent invention; in which a marking M is formed using a laser beam Lin the intermediate layer of a key top 1 in FIG. 2(A), in the uppermostlayer of the key top 1 in FIG. 2(B), in the lowermost layer of the keytop 1 in FIG. 2(C) and in a printing layer on the rear face of the keytop in FIG. 2(D);

FIG. 3 is a block diagram showing the generalized flow of the productionprocess which is common to each of embodiments of the present inventionirrespective of the technique of forming characters;

FIG. 4 is a plan view illustrating an example of key unit to be formedin Block S3 “Forming basic characters” in the production process shownin FIG. 3;

FIG. 5 shows schematic diagrams explaining stepwise the marking step toapply marking onto the top faces of key tops resorting to impregnationprinting in a fifth embodiment; in which FIG. 5(A) shows a state where arelease paper 16 is brought above in the vicinity of an assembled keyunit K; FIG. 5(B) shows a state where the release paper 16 is bonded tothe key tops 2 by thermo compression bonding; and FIG. 5(C) shows astate where impregnation printing is completed;

FIG. 6 is an enlarged cross-sectional view showing a state where markingis applied to the top face of a key top shown in FIG. 5 by impregnationprinting;

FIG. 7 is a diagram showing an example of characters and symbols of aspecific language (Arabic) formed on the top face of each key top inBlock S6 “Forming language specific characters” in the process shown inFIG. 3;

FIG. 8 shows schematic diagrams explaining stepwise the marking step toapply marking onto the top faces of key tops resorting to impregnationprinting;

FIG. 9 is an enlarged cross-sectional view showing a state where markingis applied to the top face of a key top by impregnation printing;

FIG. 10 is a block diagram showing the flow of the production processaccording to the method of an eighth embodiment;

FIG. 11 is a plan view of a key unit to be formed in Block S4“Assembling” in the production process;

FIG. 12 is a schematic diagram of means, explaining “Marking” S6 in FIG.10 to irradiate a laser beam onto the top face of each key top;

FIG. 13 is an enlarged cross-sectional view showing a state wheremarking is applied to the top face of a key top by irradiation of alaser beam;

FIG. 14 shows examples of characters and symbols of a specific language(Arabic) and numerical characters and the like which are not related tothe relevant language formed on the top faces of the respective keytops;

FIG. 15 is a plan view of a key unit to be formed in Block S4“Assembling” (see FIG. 10) in the production process according to aninth embodiment;

FIG. 16 is an enlarged cross-sectional view showing a state whereapplication of marking is achieved by irradiating a laser beam onto thetop face of a key top covered with a multilayer film which can beprinted on by laser beam irradiation;

FIG. 17 is a schematic diagram showing the constitution of themultilayer film which can be printed on by irradiation of a laser beam;

FIG. 18 is a block diagram showing the flow of the production processaccording to the technique of a tenth embodiment;

FIG. 19 is a plan view of a key unit to be formed in Block S3“Assembling” in the production process shown in FIG. 18;

FIG. 20 is a schematic diagram explaining a step of applying markingonto the top face of a glass key top by the blasting technique; and

FIG. 21 is an enlarged cross-sectional view showing the state wheremarking is applied to the top face of a glass key top by the blastingtechnique.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

There is shown an embodiment, in which a laser is used as marking means,and a transparent plastic is used as a key top material.

A green laser is shown in FIG. 1 as an example of laser beam L. In FIG.2, the laser beam L was focused on the lowermost stage of the region(upper layer, intermediate layer, lower layer or printing layer) withina key top 2 in which a marking M was to be applied, and the spotdiameter of the green laser was narrowed to 10 to 30 μm, followed byirradiation of the laser beam scanning along the planar forms ofcharacters, symbols and the like to be plotted. After completion ofirradiation along the plane of the first stage, the focus of the laserbeam was shifted to the stage above to repeat irradiation along theplane of that stage. Thus, irradiation was repeated predetermined timescorresponding to the number of stages to form three-dimensionalassemblages of fine carbonized black spots or of white spots consistingof cracks or foams indicating the desired characters, symbols and thelike, respectively. It should be noted here that in the case where alaser beam is irradiated onto the printing layer, neither carbonizedblack spots nor white spots are formed, but the laser beam pierces ablocking layer to form openings and exposes the color of the coloringlayer lying under it through these openings.

When marking is to be applied, the laser beam is focused on the desiredposition in a transparent plastic medium where a character, symbol orthe like is to be marked. When light energy is fed to the focus of thelaser beam, carbonization, cracking or foaming is induced in the plasticby an abrupt temperature change to form fine black spots or white spots.The focus of the laser beam is moved two-dimensionally orthree-dimensionally following the design of the character, symbol or thelike by a computer-controlled reflector system (galvanoscanner) to forman assemblage of fine carbonized black spots or white spots indicatingthe character, symbol or the like along the track of the laser beam.

As the plastic key having abrasion resistance referred to as the objectto be attained, there is given a plastic key, in which characters,symbols and the like are marked as if they are suspended in a plasticmedium inside the key top.

In the plastic key descried above, the characters, symbols and the likeare blocked from external contact or abrasion, so that the plastic keycan give perfect abrasion resistance. Further, since these characters,symbols and the like are seen through lens effect as if they aresuspended in the transparent plastic medium each in the form of anassemblage of a multiplicity of fine carbonized black spots or whitespots, the plastic key can give a novel visual effect.

In the case where the plastic key is, for example, made of a transparentpolycarbonate resin, characters, symbols and the like can be indicatedeach as an assemblage of a multiplicity of fine carbonized black spotsas if it is suspended in the transparent plastic medium.

The embodiment will be explained referring to FIG. 2. In FIG. 2, thereference mark 1 represents a silicone rubber key pad; 2, a key top madeof a transparent polycarbonate resin; 3, a dome switch; S, alight-transmitting adhesive between the key top and the key pad; L, alaser beam and M, a marking formed in the key top 2. FIGS. 2(A), 2(B),2(C) and 2(D) show a state where a marking M is applied to theintermediate layer of the key top 2, in the uppermost layer of the keytop 2, in the lowermost layer of the key top 2 and in a printing layeron the rear face of the key top, respectively. The marking M is formedthree-dimensionally over several stages along the thickness of the keytop.

Second Embodiment

In the case where the above plastic key top 2 is made, for example, of atransparent methyl polyacrylate (acrylic resin), characters, symbols,etc. can be indicated each as an assemblage of white spots formed by amultiplicity of fine cracks as if it is suspended in a transparentplastic medium.

Third Embodiment

As the laser beam, there is used either a beam with a wavelength of 1064nm, which is a fundamental wave irradiated from a Nd:YAG laser(neodymium ion-doped yttrium aluminum garnet crystal laser), a beam witha wavelength of 532 nm, which is the second harmonic wave, or a beamwith a wavelength of 355 nm, which is the third harmonic wave. Anapparatus for extracting the second harmonic wave of the Nd:YAG laser isreferred to as “an SHG YAG laser” or as “a green laser”, since the laserbeam with a wavelength of 532 nm irradiated from the apparatus presentsgreen color. FIG. 1 is a schematic diagram showing the constitution ofthe SHG YAG laser (extracted from H. Kobayashi: “LASER NO HANASHI”1992/1, THE NIKKAN KOGYO SHIMBUN, LTD.). Further, “a THG YAG laser” forextracting the third harmonic wave has substantially the sameconstitution as that shown in FIG. 1.

Fourth Embodiment

The laser equipment is not to be limited to the YAG laser. It may belasers of other solids doped with Nd ion such as glass laser and YVO₄laser or an excimer laser. Further, the higher harmonic wave is notlimited to the second harmonic wave or the third harmonic wave, butfourth or higher harmonic wave may be used if it is acceptable in termsof efficiency.

Fifth Embodiment

Another embodiment is illustrated in FIGS. 3 to 7, in which impregnationprinting is used as marking means and a transparent resin is used as thekey top material.

Since markings to be formed on the top faces of key tops are required tohave abrasion resistance, a marking method satisfying the requirementmust be used. In the present invention, the impregnation printing methodsatisfies the requirement. If impregnation printing is applied to thesurface of a hard resin key top, a printing ink seeps into the key topto a predetermined depth from the surface thereof to realize excellentabrasion resistance compared with markings formed by the conventionalprinting methods including screen printing, dispensing with formation ofa protecting layer for protecting the marked characters and the likefrom abrasion. However, since some resins have compatibility toimpregnation printing but others do not, and since some resins havesuitability for illuminated keys and others do not, an optimum materialmust be selected taking these aspects into consideration.

Polybutylene terephthalate (PBT) resin has been noted for thesuitability for impregnation printing among many other resin materialsand besides has excellent properties including abrasion resistance,chemical resistance and molding stability, so that the PBT resin is anexcellent material for forming key tops. However, since molded productsof the PBT resin are opaque white, the resin is subject to somelimitations in that it is not suitable for a design where charactersetc. printed on the rear face of the key top is seen through it from thetop face. Thus, not all resins are acceptable.

As the fifth embodiment of the present invention, there is given a casewhere a polyethylene terephthalate (PET) resin or a polyacetal (POM)resin is selected as the key top material. Both of these materials haveexcellent compatibility to impregnation printing and are transparent ortranslucent resins, and they also have sufficient surface hardness andare suitably applied to key tops of an illuminated key.

When impregnation printing is to be applied to the resin key tops moldedusing such resins, there are two possible techniques: one is the heattransfer method and the other is the direct method. In the heat transfermethod, a plastic release paper on which characters, symbols, etc. to beprinted are plotted with a special ink kneaded together with a sublimingdye is placed on the top faces of key tops and is bonded to the bycompression at a predetermined temperature for a predetermined time.Thus, the coating component contained in the ink sublimes and vaporizesto seep into the resin to a depth of 30 to 50 μm from the surface,anchoring the characters, symbols, etc. in the surface layer of each keytop.

Meanwhile, in the direct method, the same special ink as described aboveis used for printing characters, symbols, etc. directly onto the topface of each key top by means of pad printing or screen printing,followed by heat treatment under predetermined conditions. Thus, thecoating component contained in the ink sublimes and vaporizes to seepinto the resin, anchoring the characters, symbols, etc. in the surfacelayer of each key top like in the heat transfer method.

In FIG. 3, S1 is a step for forming a key pad, S2 is a step for formingkey tops, and S3 is a step for writing basic characters etc. onto thesurface of each key top, which can be skipped if it is not necessary. S4is a step for assembling a key unit by bonding the key tops to the topface of the key pad. In S5 destination or the relevant language isdetermined. S6 represents a step of writing language specific charactersand the like onto the top face of each key top.

In FIG. 4, the reference mark K represents a key unit; 1 and 1 a, keypads made of a silicone rubber or a thermoplastic elastomer; 2, a keytop; 4, a basic character and 5, language specific characters. FIG. 3 isa block diagram showing the process for producing an illuminated keyunit K according to the present invention including marking afterassembling, as described above. FIG. 4 is a plan view of the key unit Kto be formed in the block “Forming basic characters” in FIG. 3.

In the production process according to this embodiment, as shown in FIG.3, the key tops 2 and the key pad 1 are formed by injection molding inseparate steps (S1, S2) respectively, and after formation of numericalcharacters and the like (basic characters) 4 which are not related tothe relevant language (S3, which can be skipped) on the respective keytops 2, the key tops 2 and the key pad 3 are assembled by bonding themtogether with an adhesive or the like (S4). The ellipsoids or ovalsshown in FIG. 4 express key tops 2 made of a transparent hard resin, andbasic characters 4 including numerical characters and symbols are formedon the bottom faces of the respective key tops 2. These basic characters4 are formed as the markings which are not related to the relevantlanguage prior to “Determining destination” (S5) in the above blockdiagram, and in this state the process of producing the key unit 1 isinterrupted or stopped once. In FIG. 4, the basic characters 4 are seenthrough each key top 2.

When the destination is determined and those elements of characters,symbols, etc. which are related to the relevant language are defined,the process of producing the key unit K is resumed or started, and thenthe characters, symbols, etc. that are specific to the language of thedestination (language specific characters) 5 are marked on the top facesof the respective key tops 2 by impregnation printing (S6). The entireproduction process is completed by application of this final markingonto the top face of each key top 2. The key unit K thus obtained as afinished product is incorporated into a predetermined mobile device andis shipped to the destination.

FIG. 5 is a schematic diagram explaining the step of applying markingonto the top face of each key top 2 by impregnation printing. In theheat transfer method as a technique of impregnation printing, a specialrelease paper 16 having characters, symbols, etc. printed preliminarilywith a subliming ink on a plastic film is used. (A) shows the statewhere the release paper 16 is brought above in the vicinity of theassembled key unit K; (B) shows the state where the release paper 16 isbonded to the key tops 2 by thermo compression bonding; (C) shows thestate where impregnation printing of characters, symbols, etc. 5 ontothe top face of the key top 2 is completed. FIG. 6 is an enlargedcross-sectional view showing the state where marking onto the top faceof a key top 2 is applied by impregnation printing. The extent overwhich the printing ink seeps (where language specific characters, etc. 5are formed) is indicated by few broken lines drawn at the top of the keytop 2, while a printing layer (where basic characters etc. 4 are to beformed) is indicated by the heavy line drawn at the bottom of the keytop 2.

FIG. 7 shows an example of characters and symbols 5 of a specificlanguage (Arabic is shown in FIG. 7) formed on the top faces of therespective key tops 2 by application of marking after determination ofthe destination (the basic characters 4 formed on the bottom faces ofthe key tops 2 are also seen).

Sixth Embodiment

As an alternative to the fifth embodiment described above, there isshown a case where a polycarbonate (PC) resin is selected as the key topmaterial. The PC resin is widely used for making key tops of key unitsfor mobile devices, and it is as it were a commonly used material.However, the PC resin involves a problem that it has rather insufficientsurface hardness, because it is a noncrystalline resin. Therefore, ifimpregnation printing is directly applied to the surface of the PC resinkey top, the impregnating ink can be rubbed off as the resin surfacewears.

Thus, in the case of the PC resin, the surface of the key top is coveredbeforehand with a protecting coating layer having high abrasionresistance, and impregnation printing is applied to this layer. As thematerial of the protecting coating layer, there may be used, forexample, a polyurethane-acrylate series UV-curing resin (UV coatingagent). Although it is, of course, conceivable to form a protectingcoating layer after impregnation printing, the technique of forming theprotecting coating layer preliminarily before determination of thedestination, as described above, meets the objects of the presentinvention.

Seventh Embodiment

An alternative to the fifth and sixth embodiments is shown in FIGS. 8and 9. In this alternative process for producing a key unit, apolybutylene terephthalate (PBT) resin film or a film of a mixture of aPBT resin and a polycarbonate (PC) resin is used as the key top materialand is molded into a three-dimensional key top shape, anothertransparent resin is charged into the depression formed on the rear sideof the molded part to form a key top, and then impregnation printing ofcharacters, symbols, etc. is applied to the resin film of the key toplaminated with it.

Although the polybutylene terephthalate (PBT) resin has been noted forits high compatibility to impregnation printing among many other resinmaterials, molded products of the PBT resin are opaque white, so thatthe resin is subject to some limitations in that it is not suitable fora design where characters etc. printed on the rear face of the key topis seen through it from the top face. However, the PBT resin hasfavorable properties as the film for key tops that it shows excellentabrasion resistance, even when molded into a thin film, and excellentmoldability and that, when the resin is subjected to drawing to have athree-dimensional shape, the resulting drawing can maintain thethree-dimensional shape stably.

Thus, in this embodiment, a PBT resin is formed into a thin film(thickness: 20 to 300 μm), or a PBT resin is diluted with a PS resin andthe resulting mixture is formed into a thin film so as to dilute theinherent color (opaque white) of the PBT resin and also to makeeffective use of the properties of the PBT resin including compatibilityto impregnation printing, abrasion resistance and molding stability. Itshould be noted here that a PC resin or a mixture of a PC resin andpolystyrene (PS) resin can be given as the transparent resin for formingthe main body of the key top.

In applying impregnation printing onto the key top laminated with theabove resin film, there are two possible techniques: one is the heattransfer method and the other is the direct method. In the heat transfermethod, a special plastic release paper on which characters, symbols,etc. to be printed are plotted with a special ink kneaded together witha subliming dye is placed on the top faces of key tops and is bonded tothem by compression at a predetermined temperature for a predeterminedtime. Thus, the coating component contained in the ink sublimes andvaporizes to seep into the resin film to a depth of 30 to 50 μm from thesurface, anchoring the characters, symbols, etc. in the surface layer ofthe key top.

Meanwhile, in the direct method, the same special ink as described aboveis used for printing characters, symbols, etc. directly onto the topface of each key top by means of pad printing or screen printing,followed by heat treatment under predetermined conditions. Thus, thecoating component contained in the ink sublimes and vaporizes to seepinto the resin, anchoring the characters, symbols, etc. in the surfacelayer of the key top like in the heat transfer method.

The process in this embodiment is actually the same as shown in theprocess diagram of FIG. 3. Incidentally, referring to the referencemarks in FIG. 8, K represents a key unit; 12, a key top; 12 a, a resinfilm layer covering the key top 12; 13, a key pad; 4, a basic characterand 5, language specific characters. As described already, FIG. 3 is ablock diagram showing the process for producing an illuminated key unitK according to the present invention including marking after assembling.FIG. 4 is a plan view of the key unit K to be formed in the block“Forming basic characters” in FIG. 3.

In this production process, as shown in FIG. 3, the key tops 12 and thekey pad 13 are formed by injection molding in separate steps (S1, S2)respectively, and after formation of numerical characters and the like(basic characters) 4 which are not related to the relevant language onthe key tops 12 (S3, which can be skipped), the key tops 12 and the keypad 13 are assembled by bonding them together with an adhesive or thelike (S4). The ellipsoids or ovals shown in FIG. 4 express key tops 12each laminated with a resin film, and basic characters 4 includingnumerical characters and symbols are formed on the bottom faces of therespective key tops 12. These basic characters 4 are formed as themarkings which are not related to the relevant language prior to“Determining destination” (S5) in the above block diagram, and in thisstate the process of producing the key unit K is interrupted or stoppedonce. In FIG. 2, the basic characters M(4) are seen through the key tops12.

When the destination is determined and those elements of characters,symbols, etc. which are related to the relevant language are defined,the process of producing the key unit 1 is resumed or started, and thenthe characters, symbols, etc. that are specific to the language of thedestination (language specific characters) 5 are marked onto the topfaces of the respective key tops 2 (on the resin film layers 2 a) byimpregnation printing (S6). The entire production process is completedby application of this final marking onto the top faces of therespective key tops 2. The key unit K thus obtained as a finishedproduct is incorporated into a predetermined mobile device and isshipped to the destination.

FIG. 8 is a schematic diagram explaining the step of applying markingonto the top faces of the key tops 12 by means of impregnation printing.In the heat transfer method as a technique of impregnation printing, aspecial release paper 16 having characters, symbols, etc. printedpreliminarily with a subliming ink on a plastic film is used. FIG. 8(A)shows the state where the release paper 16 is brought above in thevicinity of the key tops 12 assembled into the key unit; FIG. 8(B) showsthe state where the release paper 16 is bonded to the key tops 12 bythermo compression bonding (e.g., at 150° C. for about 5 minutes); FIG.8(C) shows the state where impregnation printing is completed. FIG. 9 isan enlarged cross-sectional view showing the state where marking ontothe top face of a key top 2 is achieved by impregnation printing. Theextent over which the printing ink seeps into the resin film 12 a (wherelanguage specific characters, etc. 5 are formed) is indicated by theline segment drawn at the top of the resin film 12 a, while a printinglayer (where basic characters, etc. 4 are formed) is indicated by theheavy line drawn at the bottom of the key top.

FIG. 7 shows an example of characters and symbols of a specific language(Arabic is shown in FIG. 7) formed on the top faces of the key tops 2 byapplication of marking after determination of the destination (the basiccharacters 4 formed on he bottom faces of the key tops 2 are also seen).

Eighth Embodiment

While a laser is used as the marking method like in the first to fourthembodiments, what is different here is the mechanism of formingcharacters, symbols, etc. on the key tops with the laser beam. Theeighth embodiment will be explained referring to FIGS. 10 andfollowings. FIG. 10 is a block diagram showing a process for producingan illuminated key unit 21 according to the present invention includingmarking after assembling. In FIGS. 11 to 14, the reference mark 21represents a key unit; 22, a key top; 23, a key pad made of a siliconerubber or a thermoplastic elastomer; 24, a basic character; 25, languagespecific characters; and 26, a laser irradiator.

In this embodiment, the key tops 22 shown in FIG. 11 are formed, forexample, by subjecting a resin composition containing a polycarbonate(PC) resin and an adequate amount of kechene black added as an absorbentto injection molding (S1), and after a key pad 23 is formed bysubjecting a silicone rubber to injection molding (S2), the key tops 22and the key pad 23 are assembled by bonding them together with anadhesive (S4), as shown in the process diagram of FIG. 10. If necessary,a light blocking film may be formed on the upper face of the key pad 23.Since each key top 22 is a translucent or opaque gray or black moldedproduct, it is not suitable for a constitution where characters,symbols, etc. are plotted on the bottom face of the key top to be seenthrough it from the upper face. Therefore, the assembling step (S4) iscarried out without application of marking of characters etc. onto thebottom face of the key top, and the process of producing the key unit 21is interrupted once. FIG. 11 is a plan view showing the key unit 21after completion of the assembling step (S4). The reason why the entirekey unit 21 is shown as blackened is that the upper face of the key pad23 is blocked from light, and that the ellipsoid or oval key tops 22appear to be gray or black due to kechene black contained in them.

When the destination is determined and those characters, symbols, etc.which are related to the relevant language are defined, the process ofproducing the key unit 21 is resumed, and numerical characters and thelike (basic characters) 4 which are not related to the relevantlanguage, as well as, characters, symbols, etc. that are specific to thelanguage of the destination (language specific characters) 5 arecombined and are marked on the top faces of the respective key tops 22by irradiation of a laser beam (S6), as shown in FIG. 14. The entireproduction process is completed by application of this final markingonto the top faces of the key tops 22. The key unit 21 thus obtained asa finished product is incorporated into a predetermined mobile deviceand is shipped to the destination.

Incidentally, resin materials other than the PC resin suitable forforming key tops in view of heat resistance, abrasion resistance, impactresistance, etc. include POM (polyacetal) resin, ABS(acrylonitrile-butadiene-styrene copolymer) resin, HIPS (high impactpolystyrene) resin, PP (polypropylene) resin, PA (polyamide) resin, PBT(polybutylene terephthalate) resin, ABS-PBT alloy (mixed) resin andABS-PC alloy resin.

It is also possible to add to these resins suitable pigments, additives,etc. other than kechene black described above and to allow thecharacters, symbols, etc. to be marked to develop color (yellow, green,blue, orange, pink, etc.). In this case the color of characters on thekey tops can be changed from key to key depending on the function of therespective keys.

FIG. 12 is a schematic diagram explaining the step of applying markingonto the top face of the key top 22 by means of laser beam irradiation.Marking patterns M are first designed for the respective keys. Eachmarking pattern M consists of a combination of a numerical character orthe like (basic character) 24 that is not related to the relevantlanguage and language specific characters, symbols, etc. This designingis carried out for all of the keys contained in the key unit ofinterest. Next, the thus designed marking patterns for the group of keysare input into the laser irradiator 26 and are stored as digital data.The laser irradiator 26 implements, based on the stored digital data,full-automatic application of the predetermined markings onto the topfaces of the key tops 2 by correlating and controlling thethree-dimensional position (X, Y, Z coordinates) of the laser beam spotand on-off timing of laser beam irradiation.

Laser oscillating means to be employed in the laser irradiator 26 is notparticularly limited so long as it can give powers necessary forachieving marking. For example, it is possible to employ a popular CO₂laser or a YAG laser as a typical solid laser. The mode of oscillationis not critical and it may be of continuous or pulsated.

FIG. 13 is an enlarged cross-sectional side view showing the state wherea marking is applied to the top face of a key top 22 by irradiation of alaser beam. The broken lines express, for example, a character or asymbol M formed as a three-dimensional assemblage of white spots formedimmediately under the top face of the key top 22.

FIG. 14 is a plan view showing the state where application of markingonto the key unit 21 is completed after determination of thedestination. In FIG. 14, each key top 21 has on the top face acombination of a basic character 24 and characters and symbols 25 of aspecific language (Arabic is shown in FIG. 14).

Ninth Embodiment

A ninth embodiment employing key tops each covered on the surface with amultilayer film which can be printed on by irradiation of a laser beamwill be described referring to FIGS. 15 to 17 in order to produce anilluminated key unit, which has fully abrasion-resistant characters,symbols, etc. marked on it and which can be completed as soon aspossible after determination of the destination.

In the illuminated key unit according to the ninth embodiment, each keytop covered on the surface with a multilayer film, which can be printedon by irradiation of a laser beam, is bonded to a key pad made of alight-transmitting rubber or thermo-plastic elastomer (hereinafterreferred to as “light-transmitting key pad”). Then, a laser beam isirradiated upon the top face of the key top to apply marking ofpredetermine characters, symbols, etc. The thus marked characters,symbols, etc. neither come off nor disappear even by application offriction, realizing excellent abrasion resistance.

As the multilayer film which can be printed on by irradiation of a laserbeam, for example, the one as disclosed in the pamphlet of PCTPublication No. 02/30677 (WO0230677) can be used, as mentioned already.In the pamphlet, a film having a multilayer structure is disclosed, andthe film contains a transparent plastic film having on the lower face ametal vapor-deposited film, and a colored layer formed with somedistance secured from the metal vapor-deposited film.

In the process of producing the key unit, the production is interruptedor stopped once to form a semi-finished product in the state where allof the steps including assembling which are implementable withoutdetermination of the destination are finished. More specifically, thekey tops each covered on the surface with the multilayer film are bondedto the light-transmitting key pad to complete assembling of the keyunit. For the semi-finished product, what is remaining in this state isonly the step of applying marking onto the top face of each key top.Final marking of characters including the characters, symbols, etc.which are related to the destination is carried out, as soon as they aredefined, by irradiating a laser beam onto the top surface of the keytop, and thus each key unit can be completed in the shortest period oftime after determination of the destination.

The process diagram showing the process of producing the illuminated keyunit is the same as that of the eighth embodiment shown in FIG. 10. FIG.17 is a schematic diagram showing the constitution of the multilayerfilm 2 a. In FIG. 17, the reference marks 37, 38 and 39 represent theplastic film, the metal vapor-deposited film and the colored layer inthe multilayer film 2 a, respectively.

The multilayer film 2 a which can be printed on by irradiation of alaser beam will be described referring to FIG. 17. A 50 μm-thickpolyethylene terephthalate (PET) film was used as the plastic film 37,and a 100 nm-thick aluminum vapor-deposited film 38 was formed on thelower side of the film 37 through a 10 μm-thick protecting and coloringlayer 40 (for coloring the armor). Further, a 10 μm-thick transparent orcolored transparent protecting and coloring layer 41, a 200 μm-thickadhesive layer 42, a 10 μm-thick colored layer 39 (for givingcharacters) and a 50 μm-thick PET resin film 37 a were built upsuccessively on the lower side of the vapor-deposited film 38.

A key top 2 was formed by subjecting the multilayer film 2 a to stampingto form an outer shape of the key top 2 as shown in FIG. 4, and then atransparent hard resin 10 such as a polycarbonate (PC) resin and a PETresin was charged into the depression formed on the rear side of theouter shape.

The process diagram of this embodiment is the same as that shown in FIG.10. Key tops 2 and a key pad 1 are formed in separate steps (Steps S1,S2) respectively, and they are assembled by bonding them together withan adhesive and the like (Step S4). If necessary, a light-blocking filmmay be formed on the top face of the key pad 1. The surface of each keytop 2 is covered with the opaque multilayer film 2 a except for theportions printed by irradiation of a laser beam onto the top face, sothat the key top 2 is not suitable for the constitution wherecharacters, symbols, etc. are plotted on the bottom face of the key topto be seen through it from the upper face. Therefore, the assemblingstep (S4) is carried out without application of marking of charactersand the like on the bottom face of the key top 2, and in this state theprocess of producing the key unit K is interrupted once to provide asemi-finished product.

If the same marking means is employed, plural kinds of key tops ifpresent can be treated by it by controlling the movement with themarking means (by controlling delicately the movement of the markingmeans within the same step). For example, in the case where blasting isemployed as the marking means, it is possible to treat both resin keytops and glass key tops, even if they are commingled. In the case wherelaser machining is used as the marking means, it is possible to treatfilm key tops, keys to be marked by blackening or whitening and keys tobe marked by multi color development, even if they are commingled.

FIG. 15 is a plan view of the key unit 1 showing the state where theassembling step (S4) is completed. The ellipsoids or ovals shown in FIG.15 express unmarked key tops.

When the destination is determined and those characters, symbols, etc.which are related to the relevant language are defined, the process ofproducing the key unit K is resumed, and numerical characters and thelike-(basic characters) 4 which are not related to the relevantlanguage, as well as, the characters, symbols, etc. that are specific tothe language of the destination (language specific characters) 5 arecombined and are marked on the top faces of the key tops 22 byirradiation of a laser beam (S6), as shown in FIG. 7. The entireproduction process is completed by application of this final markingonto the top faces of the key tops 2. The key unit K thus obtained as afinished product is incorporated into a predetermined mobile device andis shipped to the destination.

The process diagram of applying making onto the top face of the key top2 by irradiation of a laser beam is the same as that shown in FIG. 12.First, marking patterns to be marked on the top faces of the key tops 2are first designed respectively. Each marking pattern consists of acombination of a numerical character or the like (basic character) 4that is not related to the relevant language and language specificcharacters, symbols, etc. This designing may be carried out at a timefor all of the keys contained in the key unit of interest. Next, thethus designed marking patterns for the group of keys are input into thelaser irradiator 26, shown in FIG. 12, and are stored as digital data.The laser irradiator 26 implements, based on the stored digital data,full-automatic application of the predetermined markings onto the topfaces of the respective key tops 22 by correlating and controlling thethree-dimensional position (X, Y, Z coordinates) of the laser beam spotand on-off timing of laser beam irradiation.

Laser oscillating means to be employed in the laser irradiator 26 is notparticularly limited so long as it can give powers necessary forachieving marking. For example, it is possible to employ the popular CO₂laser or a YAG laser as a typical solid laser. The mode of oscillationis not critical and it may be of continuous or pulsated.

FIG. 16 is an enlarged cross-sectional side view showing the state wheremarking is applied to the top face of a key top 2 by irradiation of alaser beam. The double line drawn in the multilayer film 2 a coveringthe key top 2 expresses the position of the marking containing acombination (4+5) of a basic character 4 and characters and symbols 5 ofa specific language.

The key unit K having gone through the marking after determination ofthe destination is of the same state as shown in FIG. 7, illustratingcombinations of basic characters 4 and language specific characters 5(Arabic is illustrated in FIG. 7) formed on the top faces of the keytops 2, respectively.

Tenth Embodiment

While a tenth embodiment is illustrated in FIGS. 18 to 21, the key unitof this embodiment is of an illuminated type, in which glass key topsare bonded onto a key pad made of a light-transmitting silicone rubberor thermoplastic elastomer. This embodiment shows as the marking methoda blasting technique to blast fine abrasive particles at a high speedagainst the top face of each glass key top. Incidentally, in attainingthe objects, the blasting technique, may be of the masked method using amask or of the maskless method using no mask.

Glass is excellent in transparency, surface hardness and abrasionresistance. According to the blasting technique, engraving and the likecan be applied to the glass surface as desired. If marking is applied byblasting onto the surface of a glass key top, characters, symbols, etc.are indicated each as a pattern formed by an assemblage of fineprotrusions and indentations (grains), which induce irregular lightreflection to give a fancy appearance. Since such grainy patterns areengraved on the surfaces of the glass key tops respectively, theyneither come off nor disappear, exhibiting excellent abrasionresistance.

In the process of producing the key unit of interest, the production isinterrupted or stopped once in the state where all of the stepsincluding assembling which are implementable without determination ofthe destination are finished. More specifically, marking of numericalcharacters and the like which are not related to the relevant languageis finished and the glass key tops and the light-transmitting key padare bonded together to complete assembling of the key unit. What isremaining in this state is only the step of applying marking onto thetop face of each key top. Then, as soon as the elements of charactersand symbols related to the destination are defined, the final marking isapplied by means of blasting.

However, if the masked blasting technique is employed here, in whichportions on the surface of the target glass key top to be left unmarked(where no characters, symbols, etc. are to be marked) are protected withmasks, it takes time for forming the masks, and the object of thepresent invention cannot be fully attained. Therefore, it is desirableto employ the maskless blasting technique using no mask. This realizesthe production process that can complete the key units in the shortestperiod of time after determination of the destination and also attainsthe objects.

FIG. 18 is a block diagram showing the flow of the process of producingthe illuminated key unit according to the present invention. FIG. 19 isa plan view of the key unit 1 to be formed in the block “Forming basiccharacters” in FIG. 18. In FIGS. 19 and 20, the reference mark 1represents a key unit; 2, a glass key top; 3, a light-transmitting keypad; 4, a basic character; 5, language specific characters; 46, anautomatic marking system; and 47, a blasting equipment.

In the process shown in FIG. 18, the glass key tops 2 and thelight-transmitting key pad 1 shown in FIG. 19 are formed in separatesteps (S1, S2) respectively, and after formation of numerical charactersand the like (basic characters) 4 which are not related to the relevantlanguage, for example, on the bottom face of each glass key top 2 bymeans of printing, engraving, blasting, etc. (S3), the glass key tops 2and the light-transmitting key pad 1 are assembled by bonding themtogether with an adhesive and the like (S4). The ellipsoids or ovalsshown in FIG. 19 express the glass key tops 2 of the respective keys,and basic characters 4 including numerical characters and symbols areformed on the bottom faces of the respective key tops 2. These basiccharacters 4 are formed as the markings which are not related to therelevant language prior to “Determining destination” (S5) in the aboveblock diagram, and in this state the process of producing the key unit Kis interrupted once.

In FIG. 19, the basic characters 4 are seen through the respective glasskey tops 2. It should be noted here that both the basic characters 4 andthe language specific characters 5 can be marked altogether on the topfaces of the respective glass key tops 2 after determination of thedestination. In this case, the step 3 is skipped, and the processproceeds to the assembling step S4 with the glass key tops 2 remainingunmarked.

When the destination is determined and those elements of characters,symbols, etc. which are related to the relevant language are defined,the process of producing the key unit K is resumed, and the characters,symbols, etc. that are specific to the language of the destination(language specific characters) 5 are marked on the top faces of the keytops 2 by means of blasting (S6). The entire production process iscompleted by application of this final marking onto the top face of eachglass key top 2. The key unit K thus obtained as a finished product isincorporated into a predetermined mobile device and is shipped to thedestination.

FIG. 20 is a schematic diagram explaining the step of applying markingonto the top face of each glass key top 2 by means of maskless blasting.First, language specific characters, symbols, etc. 5 to be marked on thetop faces of the glass key tops 2 are designed using a CAD machine andthe like. This designing is carried out at a time for all of the keyscontained in the key unit of interest. Next, the thus designed markingpatterns for the respective glass key tops 2 are input into theautomatic marking system 46 and are stored as digital data. Theautomatic marking system 46 implements, based on the stored digitaldata, full-automatic application of the predetermined markings onto thetop faces of the respective glass key tops 2 by correlating andcontrolling the plan position of a nozzle (X, Y coordinates of thenozzle tip) of the blasting equipment 47 and on-off timing of blastingan abrasive.

Referring to the blasting equipment 47, for example, “the powderinjecting apparatus” disclosed in Unexamined Japanese Patent Publication(Kokai) No. 2000-94332 can be applied. Further, the glass key top 2 isformed by subjecting, for example, a low-melting glass having asoftening point of about 500° C. to molding, and by blasting, forexample, spherical steel beads against it as the abrasive.

The same arrangement as shown in FIG. 7 applies to the characters andsymbols 5 of a specific language (Arabic in FIG. 7) formed on the topfaces of the respective glass key tops 2 (basic characters 4 can alsobee seen).

Eleventh Embodiment

In an eleventh embodiment, a hard resin is selected as the material ofthe key unit. More specifically, there is disclosed an illuminated keyunit having a key pad made of a light-transmitting soft rubber orthermoplastic elastomer (hereinafter referred to as “light-transmittingkey pad”) and hard resin key tops. There is selected the blastingtechnique as the marking method, in which fine abrasive particles areblasted at a high speed against the top faces of the hard resin keytops. Incidentally, in attaining the objects, the blasting technique maybe of the masked method using a mask or of the maskless method using nomask.

(Common Element)

As the hard resin material for forming the key tops, suitably used arethose capable of giving molded articles showing transparency and highsurface hardness. Such materials nonlimitatively include, for example,polyethylene terephthalate (PET) resins, polyarylate (PAR) resins,polyacrylate (PMMA, PAA) resins, polypropylene (PP) resins, high impactpolystyrene (HIPS) resins and styrene-acrylonitrile (SAN) copolymerresins. Meanwhile, according to the blasting technique, engraving andthe like can be applied as desired onto the surfaces of hard resinmolded articles. If marking is applied to the surface of a hard resinkey top by the blasting technique, characters, symbols, etc. can beindicated each as a pattern formed by an assemblage of fine protrusionsand indentations (grains), which induce irregular light reflection togive a fancy appearance. Since such grainy patterns are engraved on thesurfaces of the hard resin key tops respectively, they neither come offnor disappear, exhibiting excellent abrasion resistance.

With a view to attaining the objects of the present invention, in theprocess of producing the key unit of interest, the production isinterrupted or stopped once in the state where all of the stepsincluding assembling which are implementable without determination ofthe destination are finished. More specifically, marking of numericalcharacters and the like which are not related to the relevant languageis finished and the hard resin key top and the light-transmitting keypad are bonded together to complete assembling of the key unit. What isremaining in this state is only the step of applying marking onto thetop face of each key top. Then, as soon as those elements of charactersand symbols which are related to the destination are defined, the finalmarking is applied by means of blasting.

However, if the masked blasting technique is employed here, in whichportions on the surface of the target hard resin key top to be leftunmarked (where no characters, symbols, etc. are to be marked) areprotected with masks, it takes time for forming the masks, and theobjects of the present invention cannot be fully attained. Therefore, itis desirable to employ the maskless blasting technique using no mask.This realizes the production process that can complete the key units inthe shortest period of time after determination of the destination andalso attains the objects of the present invention.

The block diagram showing the flow of the process of producing theilluminated key unit according to this embodiment is the same as thatshown in FIG. 18. Further, the plan view of the key unit K to beproduced in the block “Forming basic characters” in FIG. 18 is as shownin FIG. 19. The reference mark K represents a key unit; 2, a hard resinkey top; 1, a light-transmitting key pad; 4, a basic character; 5,language related characters; 46, an automatic marking system; and 47, ablasting equipment.

In FIG. 18, the hard resin key tops 2 and the light-transmitting key pad1 are formed in separate steps (S1, S2) respectively, and after printingof numerical characters and the like (basic characters) 4 which are notrelated to the relevant language, for example, on the bottom faces ofthe respective hard resin key tops 2 (S3), the hard resin key tops 2 andthe light-transmitting key pad 1 are assembled by bonding them togetherwith an adhesive and the like (S4). The ellipsoids or ovals shown inFIG. 19 express the hard resin key tops 2 of the respective keys, andbasic characters 4 including numerical characters and symbols are formedon the bottom faces of the respective key tops 2.

These basic characters 4 are formed as the markings which are notrelated to the relevant language prior to “Determining destination” (S5)in the above block diagram, and in this state the process of producingthe key unit 1 is interrupted once. In FIG. 19, the basic characters 4are seen through the respective key tops 2. It should be noted here thatboth the basic characters 4 and the language specific characters 5 canbe marked altogether on the top faces of the respective hard resin keytops 2 after determination of the destination. In this case, the step 3is skipped, and the process proceeds to the assembling step S4 with thehard resin key tops 2 remaining unmarked.

When the destination is determined and those elements of characters,symbols, etc. which are related to the relevant language are defined,the process of producing the key unit K is resumed, and the characters,symbols, etc. that are specific to the language of the destination(language specific characters) 5 are marked on the top faces of therespective key tops 2 by means of blasting (S6). The entire productionprocess is completed by application of this final marking onto the topface of each hard resin key top 2. The key unit 1 thus obtained as afinished product is incorporated into a predetermined mobile device andis shipped to the destination.

FIG. 20 is a schematic diagram explaining the step of applying markingonto the top face of each hard resin key top 2 by means of masklessblasting. First, language specific characters 5 to be marked on the topfaces of the hard resin key tops 2 are designed using a CAD machinerespectively. This designing is carried out at a time for all of thekeys contained in the key unit of interest. Next, the thus designedmarking patterns for the respective hard resin key tops 2 are input intothe automatic marking system 46 and are stored as digital data. Theautomatic marking system 46 implements, based on the stored digitaldata, full-automatic application of the predetermined markings onto thetop faces of the respective hard resin key tops 2 by correlating andcontrolling the plan position of a nozzle (X, Y coordinates of thenozzle tip) of the blasting equipment 47 and on-off timing of blastingan abrasive.

Referring to the blasting equipment 47, for example, “the powderinjecting apparatus” disclosed in Unexamined Japanese Patent Publication(Kokai) No. 2000-94332 can be applied. Further, the hard resin key top 2is formed by subjecting, for example, a polyethylene terephthalate (PET)resin to injection molding, and by blasting, for example, sphericalsteel beads against it as the abrasive.

FIG. 21 is an enlarged cross-sectional view of a hard resin key top 2having a marking M applied to the top face by means of blasting. Themarks “xxx” show the character, symbols, etc. engraved on the top faceof the hard resin key top 2.

The same arrangement as shown in FIG. 7 applies to the characters andsymbols 5 of a specific language (Arabic in FIG. 7) formed by means ofblasting on the top faces of the respective hard resin key tops 2 (basiccharacters 4 are also seen together with the language specificcharacters 5).

INDUSTRIAL APPLICABILITY

According to the marking methods of the invention in the first to fourthembodiments, when laser marking of characters, symbols, etc. is appliedto the internal medium of plastic keys to be employed in portabletelephones and the like, the beam spot diameter is narrowed to increasethe density of light energy at the irradiation spot, so that marking canbe carried out speedily with the unirradiated portions being maintainedat a temperature not higher than the permissible level.

In the plastic keys according to the present invention, since thecharacters, symbols and the like are blocked from external contact orfriction, they can give perfect abrasion resistance. Besides, sincethese characters, symbols and the like are seen through lens effect asif they are suspended in a transparent plastic medium, the plastic keyscan give a novel visual effect.

Further, according to the present invention, since marking of necessarycharacters, symbols, etc. can be applied afterward by a single step intothe inside of transparent plastic keys finished unmarked, a novelprocess for producing key units as set forth in claim 6 can beestablished utilizing this technique. According to this novel productionprocess, the lead time from determination of the destination to shippingof products can be reduced in a wide margin to improve user service.

According to the invention of the fifth embodiment (see FIGS. 3 to 7),all of the steps which are implementable without determination of thedestination are finished beforehand. As soon as those elements ofcharacters and symbols which are related to the destination are defined,marking of these characters, symbols, etc. related to the destinationare applied to the top faces of key tops by means of impregnationprinting to complete the entire process. Therefore, the key unit can becompleted in a shortest period of time after determination of thedestination, dispensing with glut to be caused by wasteful stockproduction.

Impregnation printing can be carried out using a PET resin or a POMresin as a glass clear all-purpose resin in place of the PBT resin whoseinherent color is opaque white. Further, since neither the PET resin northe POM resin has problems in terms of abrasion resistance, these resinsdispense with the protecting layer such as a UV coating on the key topsurface.

According to the sixth embodiment (see FIGS. 3 to 7), the presentinvention can be carried out effectively by combining a PC resin withother materials to make up for rather insufficient abrasion resistanceof the PC resin and by applying impregnation printing to the thuscombined PC resin.

According to the invention of the seventh embodiment (see FIGS. 8 and9), all of the steps which are implementable without determination ofthe destination are finished beforehand. As soon as those elements ofcharacters and symbols related to the destination are defined, markingof the characters, symbols, etc. related to the destination is appliedto the top faces of key tops by means of impregnation printing tocomplete the entire process. Therefore, the key unit can be completed ina shortest period of time after determination of the destination.

The invention as set forth in claim 1 can be carried out effectively byforming a PBT resin into a thin film or by diluting a PBT resin with aPS resin and then forming the resulting mixture into a thin film todilute the inherent color (opaque white) of the PBT resin and also tomake effective use of compatibility to impregnation printing, abrasionresistance, etc. of the PBT resin. In this case, the PBT resin film orthe film of a mixture of PBT resin and PC resin has no problem in termsof abrasion resistance, these films dispense with the protecting layeron the key top surface such as a UV coating.

According to the invention of the eighth embodiment (see FIGS. 10 to14), predetermined characters, symbols, etc. are marked by irradiationof a laser beam in the internal portion of each key top made of a resincomposition which develops color by laser beam irradiation, thesecharacters, symbols, etc. neither come off nor disappear even byapplication of friction and the like, realizing excellent abrasionresistance.

Further, all of the steps which are implementable without determinationof the destination are finished beforehand. As soon as characters,symbols, etc. related to the destination are defined, marking of thecharacters, symbols, etc. specific to the language of the destinationare applied by means of laser beam irradiation onto the top faces of keytops together with numerical characters and the like which are notrelated to the relevant language to complete the entire process.Therefore, the key unit can be completed in a shortest period of timeafter determination of the destination.

According to the constitution of the key unit of the invention of theninth embodiment (see FIGS. 15 to 17), by irradiating a laser beam ontothe top face of each key top, necessary characters, symbols, etc. aremarked inside a multilayer film covering each key top, so that thesecharacters, symbols, etc. neither come of nor disappear even byapplication of friction and the like, realizing excellent abrasionresistance.

According to the production process of the present invention, all of thesteps implementable without determination of the destination arefinished beforehand to provide a semi-finished product. As soon as thoseelements of characters, symbols, etc. which are related to thedestination are defined, marking of the necessary characters, symbols,etc. are applied by means of laser beam irradiation onto the top facesof key tops to complete the entire process. Therefore, the key unit canbe completed in a shortest period of time after determination of thedestination.

According to the invention of the tenth embodiment (see FIGS. 18 to 21),characters, symbols, etc. are engraved by means of blasting on the topface of each glass key top which is excellent in transparency, surfacehardness and abrasion resistance each as a pattern formed by anassemblage of fine protrusions and indentations (grains) to give a fancyappearance. Since such grainy patterns neither come off nor disappear,exhibiting excellent abrasion resistance.

According to this invention, all of the steps which are implementablewithout determination of the destination are finished beforehand. Assoon as those elements of characters, symbols, etc. which are related tothe destination are defined, marking of the characters, symbols, etc.related to the destination are applied by means of blasting against thetop faces of the glass key tops to complete the entire process.Therefore, the key unit can be completed in a shortest period of timeafter determination of the destination.

According to the invention of the eleventh embodiment (see FIGS. 18 to21), characters, symbols, etc. are engraved on the top face of each hardresin key top which is excellent in transparency, surface hardness andabrasion resistance by means of blasting each as a pattern formed by anassemblage of fine protrusions and indentations (grains) to give a fancyappearance. Since such grainy patterns neither come off nor disappear,exhibiting excellent abrasion resistance.

According to this invention, all of the steps which are implementablewithout determination of the destination are finished beforehand. Assoon as those elements of characters, symbols, etc. which are related tothe destination are defined, marking of these characters, symbols, etc.related to the destination are applied by means of maskless blastingonto the top faces of the respective hard resin key tops to complete theentire process. Therefore, the key unit can be completed in a shortestperiod of time after determination of the destination.

1. A process for producing a key unit, comprising: assembling the keyunit, which includes a resin key top made of a light-transmittingmaterial; interrupting or stopping the process for producing the keyunit once all steps in the process, including the assembling, which areimplementable without determination of a destination of the key unit arefinished, wherein said assembling comprises applying generic markingsnot specific to the destination to a back face of the key top; and afterthe destination is determined and specific markings, which are specificto a language related to the determined destination, are defined,applying the specific markings to a top face of the key top to completethe key unit.
 2. The process according to claim 1, wherein the specificmarkings are applied by impregnation printing.
 3. The process accordingto claim 2, wherein the light-transmitting resin is one of apolyethylene terephthalate (PET) resin and a polyacetal (POM) resin, andwherein the impregnation printing is applied directly onto the top faceof the resin key top.
 4. The process according to claim 2, wherein thelight transmitting resin is a polycarbonate (PC) resin, and wherein theimpregnation printing is applied to a protecting coating layer formedbeforehand on a surface of the resin key top.
 5. The process accordingto claim 2, wherein the resin key top is laminated with a resin film. 6.The process according to claim 1, wherein applying the specific markingscomprises: intermittently irradiating a laser beam having a wavelengthof 1064 nm or less in one of the infrared region, the visible region,and the near ultraviolet region, while focusing the laser beam on adesired position inside the key top to form, in the light-transmittingresin, one of an assemblage of a multiplicity of fine carbonized blackspots and an assemblage consisting of white spots consisting of amultiplicity of fine cracks or foams.
 7. The process according to claim6, wherein the laser beam is one of: a beam with a wavelength of 1064nm, which is the fundamental wave of a Nd:YAG laser; a beam with awavelength of 532 nm, which is the second harmonic wave of the Nd:YAGlaser; and a beam with a wavelength of 355 nm, which is the thirdharmonic wave of the Nd:YAG laser.
 8. The process according to claim 1,wherein the key top is made of a light-transmitting plastic, thespecific markings are applied as if they are suspended in the lighttransmitting plastic, and each of the specific markings is one of anassemblage consisting of a multiplicity of fine carbonized black spotsand an assemblage of white spots formed by cracking, and is formed byintermittently irradiating to the key top a laser beam having awavelength of 1064 nm or less in one of the infrared region, the visibleregion, and the near ultraviolet region, while focusing the laser beamon a desired position inside the key top.
 9. The process according toclaim 1, wherein the markings include at least one of a character and asymbol.
 10. A process for producing an illuminated key unit, comprising:assembling the key unit, which comprises a light-transmitting glass keytop and a key pad made of a light-transmitting rubber or elastomer;interrupting or stopping the process for producing the key unit once allsteps in the process, including the assembling, which are implementablewithout determination of a destination of the key unit are finished,wherein said assembling comprises applying generic markings not specificto the destination to a back face of the key top; and after thedestination is determined and specific markings, which are specific to alanguage related to the determined destination, are defined, applyingthe specific markings to a top face of the key top by maskless blasting,which comprises blasting fine abrasive particles at a high speeddirectly against a top face of the glass key top, to complete the keyunit.
 11. The process according to claim 10, wherein the markingsinclude at least one of a character and a symbol.
 12. A process forproducing an illuminated key unit, comprising: assembling the key unit,which comprises a light-transmitting hard-resin key top and a key padmade of a light-transmitting rubber or elastomer; interrupting orstopping the process for producing the key unit once all steps,including the assembling, which are implementable without determinationof a destination of the key unit are finished, wherein said assemblingcomprises applying generic markings not specific to the destination to aback face of the key top; and after the destination is determined andspecific markings, which are specific to a language related to thedetermined destination, are defined, applying the specific markings to atop face of the key top by of maskless blasting, which comprisesblasting fine abrasive particles at a high speed directly against thetop face of the hard resin key top, to complete the key unit.
 13. Theprocess according to claim 12, wherein the markings include at least oneof a character and a symbol.